| 摘要 |
PURPOSE:To realize the optimum controlled condition of an electric discharge lamp not only during preheating control but also during light adjustment control by mainly controlling switching frequencies of switching transistors during preheating, while mainly controlling the ON period ratio between the switching transistor/during light adjustment. CONSTITUTION:A series circuit comprising first and second switching transistors Q1, Q2, both made of power MOSFETs is connected to two ends of a DC power source E1, and the power-source-side terminals of filaments in an electric discharge lamp lare connected respectively to two ends of the first switching transistor Q1 via a coupling capacitor C1 and via a current-limiting and resonating inductor L. Furthermore, a preheating-current transmitting and resonating capacitor C2 is connected parallelly between the non-power-source-side terminals of the filaments in the electric discharge lamp l. And during preheating the ON periods of the first and second switching transistors Q1, Q2 are equalized approximately to each other for mainly controlling the switching frequencies of the transistors, while during light adjustment the ON period ratio between the first and second transistors Q1, Q2 is mainly controlled. The optimum controlled condition of the lamp can thus be realized not only during preheating control but also during light adjustment control. |
